Why didn't catherine of aragon's daughter become queen?

Matilda was the daughter of King Henry I. When King Henry I died, Matilda was his only surviving heir (his other children had died earlier on). Matilda was supposed to be the Queen of England but refused to be crowned because she thought it would lower her dignity as all the previous Queens had only been named Queen because they were married to a king. She said that she was to be called 'the lady of the english'. Matilda ruled England for a few months until her cousin Stephen Blois took the throne from her and was named King Stephen of England.